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Focus temp guage

I have had a focus for about 12 months now its the 1.8 petrol 2004 facelift model :)

I have a odd problem with the temp needle on the dash. Whenever at 30mph and I put the heater on the temp needle gradually drops but never lower than 25% roughly. If I turn it off it goes back up slowly. It does not over heater.

I have checked the return pip from to the coolant tank and the waterpump is sending back coolant happily and rapidly.

What makes this weird is at 70mph and using the heater I get no abnormalities as with at 30. If it was a stat issue would this not be the same at 70 ?

There is a coolant sensor on the back left of the block. Wiring is in tact. I wonder if the stat is sticking perhaps but I guess it would do it at 70 ?

Any ideas what might be causing this odditiy ?

Cheers

Reply to
Jeff
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The description of your fault screams 'thermostat' to me.

At 30mph, the engine isn't working hard. Putting the heater on pulls more heat from the system, which would normally cause the 'stat to close partially, and would allow the system to maintain temperature.

At higher speeds, there is sufficient heat being created to not need the 'stat to close to maintain working temperature.

Chris

Reply to
Chris Whelan

Sounds likely that's the problem and a thermostat is cheap and easy to change.

Reply to
Rob

Just another thought

Not knowing what the impeller of the water pump is constructed from, on these cars, if it is plastic the same symptoms will apply,(the impeller can split and slip/spin on the shaft) but change the thermostat first.

Have seen a few cars with this problem finally diagnosed back to the water pump. VW's are easy as they have a sensor on each side of the water pump.

Reply to
Rob

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